Aft flowing serpentine cavities and cores for airfoils of gas turbine engines

ABSTRACT

Core assemblies for manufacturing airfoils and airfoils made therefrom having an aft flowing serpentine hybrid skin core positioned relative to a plurality of core bodies and configured to define at least one serpentine cavity within the manufactured airfoil. The aft flowing serpentine hybrid skin core extends from a root region toward a tip region in a radial direction of the manufactured airfoil and the plurality of core bodies are positioned about the aft flowing serpentine hybrid skin core to form a shielding structure to thermally shield the aft flowing serpentine hybrid skin core in the manufactured airfoil.

BACKGROUND

Illustrative embodiments pertain to the art of turbomachinery, andspecifically to turbine rotor components.

Gas turbine engines are rotary-type combustion turbine engines builtaround a power core made up of a compressor, combustor and turbine,arranged in flow series with an upstream inlet and downstream exhaust.The compressor compresses air from the inlet, which is mixed with fuelin the combustor and ignited to generate hot combustion gas. The turbineextracts energy from the expanding combustion gas, and drives thecompressor via a common shaft. Energy is delivered in the form ofrotational energy in the shaft, reactive thrust from the exhaust, orboth.

The individual compressor and turbine sections in each spool aresubdivided into a number of stages, which are formed of alternating rowsof rotor blade and stator vane airfoils. The airfoils are shaped toturn, accelerate and compress the working fluid flow, or to generatelift for conversion to rotational energy in the turbine.

Flow across the airfoil tip may affect gas turbine engine performance.Clearance, abrasion and temperature effects are of concern proximate thetip region of the airfoil.

BRIEF DESCRIPTION

According to some embodiments, core assemblies for manufacturingairfoils of gas turbine engines are provided. The core assembliesincludes an aft flowing serpentine hybrid skin core positioned relativeto a plurality of core bodies and configured to define at least oneserpentine cavity within the manufactured airfoil. The aft flowingserpentine hybrid skin core extends from a root region toward a tipregion in a radial direction of the manufactured airfoil and theplurality of core bodies are positioned about the aft flowing serpentinehybrid skin core to form a shielding structure to thermally shield theaft flowing serpentine hybrid skin core in the manufactured airfoil.

In addition to one or more of the features described herein, or as analternative, further embodiments of the core assembly may include thatthe plurality of core bodies includes a radial flow core located axiallyforward the aft flowing serpentine hybrid skin core.

In addition to one or more of the features described herein, or as analternative, further embodiments of the core assembly may include thatthe aft flowing serpentine hybrid skin core includes a first upward passcore, a first downward pass core, and a second upward pass core.

In addition to one or more of the features described herein, or as analternative, further embodiments of the core assembly may include thatthe first upward pass core is a hybrid skin core and the first downwardpass core and the second upward pass core are convention cores.

In addition to one or more of the features described herein, or as analternative, further embodiments of the core assembly may include thatthe aft flowing serpentine hybrid skin core includes structures to forminternal convective heat transfer augmentation features within a cavityformed thereby.

In addition to one or more of the features described herein, or as analternative, further embodiments of the core assembly may include thatthe internal convective heat transfer augmentation features include atleast one of trip strips, turbulators, pin fins, or pedestals.

In addition to one or more of the features described herein, or as analternative, further embodiments of the core assembly may include thatthe plurality of core bodies comprise having a pressure side hybrid skincore having a first trunk and a first branch that extends from the firsttrunk, a suction side hybrid skin core spaced apart from the pressureside hybrid skin core, a leading edge hybrid skin core iscircumferentially located between the pressure side and the suctionside, and a radial flow core located between the pressure side hybridskin core, the suction side hybrid skin core, and the leading edge.

In addition to one or more of the features described herein, or as analternative, further embodiments of the core assembly may include thatthe radial flow core includes a radial core that is disposed generallyparallel to at least one of the pressure side hybrid skin core, thesuction side hybrid skin core, and the leading edge hybrid skin core,wherein the radial core is positioned between the aft flowing serpentinehybrid skin core and the leading edge hybrid skin core.

In addition to one or more of the features described herein, or as analternative, further embodiments of the core assembly may include thatthe radial flow core includes a radial diffusing tip flag core thatextends from the radial core in a direction away from the leading edgehybrid skin core and is positioned radially above the aft flowingserpentine hybrid skin core.

In addition to one or more of the features described herein, or as analternative, further embodiments of the core assembly may include thatthe radial diffusing tip flag core has an increasing radial heightdimension as the radial diffusing tip flag core extends away from theradial flow core, and the aft flowing serpentine hybrid skin coredecreases in radial height as the radial height dimension increases.

In addition to one or more of the features described herein, or as analternative, further embodiments of the core assembly may include thatthe aft flowing serpentine hybrid skin core includes a structure to forma trailing edge slot in the manufacturing airfoil.

According to some embodiments, airfoils for gas turbine engines areprovided. The airfoils have an airfoil body having a leading edge, atrailing edge, a root region, and a tip region, wherein a direction fromthe root region to the tip region is a radial direction and a directionfrom the leading edge to the trailing edge is an axial direction; ahybrid aft flowing serpentine cavity formed within the airfoil body anddefining a cooling flow path within the airfoil body and defining acooling flow path extending between a root region to a tip region of theairfoil; and a plurality of cooling cavities formed within the airfoilbody and positioned about the hybrid aft flowing serpentine cavity toform a shielding structure within the airfoil body forward of the hybridaft flowing serpentine cavity.

In addition to one or more of the features described herein, or as analternative, further embodiments of the airfoil may include that theplurality of cooling cavities includes a radial flow cavity locatedaxially forward the hybrid aft flowing serpentine cavity.

In addition to one or more of the features described herein, or as analternative, further embodiments of the airfoil may include that thehybrid aft flowing serpentine cavity includes a first upward pass, afirst downward pass, and a second upward pass.

In addition to one or more of the features described herein, or as analternative, further embodiments of the airfoil may include that thefirst upward pass core is a hybrid skin core cavity and the firstdownward pass and the second upward pass are conventional cavities.

In addition to one or more of the features described herein, or as analternative, further embodiments of the airfoil may include that thehybrid aft flowing serpentine cavity includes internal convective heattransfer augmentation features.

In addition to one or more of the features described herein, or as analternative, further embodiments of the airfoil may include that theinternal convective heat transfer augmentation features include at leastone of trip strips, turbulators, pin fins, or pedestals.

In addition to one or more of the features described herein, or as analternative, further embodiments of the airfoil may include that theplurality of cooling cavities have a pressure side hybrid skin corecavity located within the airfoil body on a pressure side relative tothe hybrid aft flowing serpentine cavity, a suction side hybrid skincore cavity spaced apart from the pressure side hybrid skin core cavityand located within the airfoil body on a suction side relative to thehybrid aft flowing serpentine cavity, a leading edge hybrid skin corecavity is circumferentially located between the pressure side and thesuction side; and a radial flow core located between (1) the pressureside hybrid skin core and the suction side hybrid skin core and (2)between the leading edge hybrid skin core cavity and the hybrid aftflowing serpentine cavity.

In addition to one or more of the features described herein, or as analternative, further embodiments of the airfoil may include that theradial flow core cavity defines a flow cavity that is generally parallelto at least one of the pressure side hybrid skin core cavity, thesuction side hybrid skin core cavity, and the leading edge hybrid skincore cavity.

In addition to one or more of the features described herein, or as analternative, further embodiments of the airfoil may include a trailingedge slot fluidly connected to the hybrid aft flowing serpentine cavityat the trailing edge of the airfoil body.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 is a schematic cross-sectional illustration of a gas turbineengine;

FIG. 2 is a schematic illustration of a portion of a turbine section ofthe gas turbine engine of FIG. 1;

FIG. 3 is a perspective view of an airfoil;

FIG. 4 is a partial perspective view of the airfoil;

FIG. 5 is a top view of the airfoil;

FIG. 6 is a partial cross-sectional view of the airfoil as viewed alongthe line 6-6 shown in FIG. 3;

FIG. 7 is a side view of a portion of an airfoil core assembly forforming a portion of the airfoil;

FIG. 8 is a first side view of an airfoil core assembly;

FIG. 9 is a second side view of the airfoil core assembly;

FIG. 10 is a perspective view of a suction side hybrid skin core;

FIG. 11 is a perspective view of a pressure side hybrid skin core;

FIG. 12 is a perspective view of a leading edge hybrid skin core;

FIG. 13 is a first side perspective view of a first arrangement of aradial flow core and a serpentine flow core;

FIG. 14 is a second side perspective view of the first arrangement ofthe radial flow core and the serpentine flow core;

FIG. 15 is a perspective view of a second arrangement of a radial flowcore;

FIG. 16 is a side perspective view of the second arrangement of theradial flow core and a serpentine flow core;

FIG. 17 is a perspective view of the suction side hybrid skin core, thepressure side hybrid skin core, and a leading edge hybrid skin core, ina shielding arrangement; and

FIG. 18 is a side perspective view of the shielding arrangement disposedabout a radial flow core and the serpentine flow core of the secondarrangement.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmentor section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flow path B in abypass duct, while the compressor section 24 drives air along a coreflow path C for compression and communication into the combustor section26 then expansion through the turbine section 28. Although depicted as atwo-spool turbofan gas turbine engine in the disclosed non-limitingembodiment, it should be understood that the concepts described hereinare not limited to use with two-spool turbofans as the teachings may beapplied to other types of turbine engines including three-spoolarchitectures.

The gas turbine engine 20 generally includes a low speed spool 30 and ahigh speed spool 32 mounted for rotation about an engine centrallongitudinal axis A relative to an engine static structure 36 viaseveral bearing systems 38. It should be understood that various bearingsystems 38 at various locations may alternatively or additionally beprovided and the location of bearing systems 38 may be varied asappropriate to the application.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a low pressure compressor 44 and a low pressureturbine 46. The inner shaft 40 is connected to the fan 42 through aspeed change mechanism, which in gas turbine engine 20 is illustrated asa geared architecture 48 to drive the fan 42 at a lower speed than thelow speed spool 30. The high speed spool 32 includes an outer shaft 50that interconnects a high pressure compressor 52 and high pressureturbine 54.

A combustor 56 of the combustor section 26 is arranged in the gasturbine engine 20. The combustor 56 is arranged between the highpressure compressor 52 and the high pressure turbine 54. An enginestatic structure 36 is arranged generally between the high pressureturbine 54 and the low pressure turbine 46. The engine static structure36 further supports bearing systems 38 in the turbine section 28.

The inner shaft 40 and the outer shaft 50 are concentric and rotate viabearing systems 38 about the engine central longitudinal axis A which iscollinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The turbines 46, 54 rotationally drive therespective low speed spool 30 and high speed spool 32 in response to theexpansion. It will be appreciated that each of the positions of the fansection 22, compressor section 24, combustor section 26, turbine section28, and fan drive gear system 48 may be varied. For example, gear system48 may be located aft of combustor section 26 or even aft of turbinesection 28, and fan section 22 may be positioned forward or aft of thelocation of gear system 48.

The gas turbine engine 20 in one example is a high-bypass gearedaircraft engine. In a further example, the gas turbine engine 20 bypassratio is greater than about six (6), with an example embodiment beinggreater than about ten (10), the geared architecture 48 is an epicyclicgear train, such as a planetary gear system or other gear system, with agear reduction ratio of greater than about 2.3 and the low pressureturbine 46 has a pressure ratio that is greater than about five. In onedisclosed embodiment, the gas turbine engine 20 bypass ratio is greaterthan about ten (10:1), the fan diameter is significantly larger thanthat of the low pressure compressor 44, and the low pressure turbine 46has a pressure ratio that is greater than about five 5:1. Low pressureturbine 46 pressure ratio is pressure measured prior to inlet of lowpressure turbine 46 as related to the pressure at the outlet of the lowpressure turbine 46 prior to an exhaust nozzle. The geared architecture48 may be an epicycle gear train, such as a planetary gear system orother gear system, with a gear reduction ratio of greater than about2.3:1. It should be understood, however, that the above parameters areonly illustrative of one embodiment of a geared architecture engine andthat the present invention is applicable to other gas turbine enginesincluding direct drive turbofans.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan section 22 of the gas turbine engine 20is designed for a particular flight condition—typically cruise at about0.8 Mach and about 35,000 feet (10,688 meters). The flight condition of0.8 Mach and 35,000 ft (10,688 meters), with the engine at its best fuelconsumption—also known as “bucket cruise Thrust Specific FuelConsumption (‘TSFC’)”—is the industry standard parameter of lbm of fuelbeing burned divided by lbf of thrust the engine produces at thatminimum point. “Low fan pressure ratio” is the pressure ratio across thefan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The lowfan pressure ratio as disclosed herein according to one non-limitingembodiment is less than about 1.45. “Low corrected fan tip speed” is theactual fan tip speed in ft/sec divided by an industry standardtemperature correction of [(T_(ram)° R)/(518.7° R)]° ⁵. The “Lowcorrected fan tip speed” as disclosed herein according to onenon-limiting embodiment is less than about 1150 ft/second (350.5 m/sec).

Although the gas turbine engine 20 is depicted as a turbofan, it shouldbe understood that the concepts described herein are not limited to usewith the described configuration, as the teachings may be applied toother types of engines such as, but not limited to, turbojets,turboshafts, and three-spool (plus fan) turbofans wherein anintermediate spool includes an intermediate pressure compressor (“IPC”)between a low pressure compressor (“LPC”) and a high pressure compressor(“HPC”), and an intermediate pressure turbine (“IPT”) between the highpressure turbine (“HPT”) and the low pressure turbine (“LPT”).

FIG. 2 is a schematic view of a portion of the turbine section 28 thatmay employ various embodiments disclosed herein. Turbine section 28includes a plurality of airfoils 60, 62 including, for example, one ormore blades and vanes. The airfoils 60, 62 may be hollow bodies withinternal cavities defining a number of channels or cores, hereinafterairfoil cores, formed therein and extending from an inner diameter 66 toan outer diameter 68, or vice-versa. The airfoil cores may be separatedby partitions within the airfoils 60, 62 that may extend either from theinner diameter 66 or the outer diameter 68 of the airfoil 60, 62. Thepartitions may extend for a portion of the length of the airfoil 60, 62,but may stop or end prior to forming a complete wall within the airfoil60, 62. Thus, each of the airfoil cores may be fluidly connected andform a fluid path within the respective airfoil 60, 62. The airfoils 60,62 may include platforms 70 located proximal to the inner diameter 66thereof. Located below the platforms 70 (e.g., radially inward withrespect to the engine axis) may be airflow ports and/or bleed orificesthat enable air to bleed from the internal cavities of the airfoils 60,62. A root of the airfoil may connected to or be part of the platform70.

The turbine section 28 is housed within a case 80, which may havemultiple parts (e.g., turbine case, diffuser case, etc.). In variouslocations, components, such as seals, may be positioned between airfoils60, 62 and the case 80. For example, as shown in FIG. 2, blade outer airseals 82 (hereafter “BOAS”) are located radially outward from the blade60. As will be appreciated by those of skill in the art, the BOAS 82 mayinclude BOAS supports that are configured to fixedly connect or attachthe BOAS 82 to the case 80 (e.g., the BOAS supports may be locatedbetween the BOAS 82 and the case 80). As shown in FIG. 2, the case 80includes a plurality of case hooks 84 that engage with BOAS hooks 86 tosecure the BOAS 82 between the case 80 and a tip of the airfoil 60.

As shown in FIGS. 3 and 4, the airfoil 60 includes an airfoil body 90having a pressure side 92, a suction side 94, a root region 96, a tipregion 98, a leading edge 100, and a trailing edge 102. The pressureside 92 is disposed opposite the suction side 94. The pressure side 92and the suction side 94 each extend radially from the root region 96toward the tip region 98. As used herein, the term “radial” refers toradial with respect to an engine axis (e.g., engine central longitudinalaxis A shown in FIG. 1). The pressure side 92 and the suction side 94each extend generally axially and/or tangentially (e.g., with respect toan engine axis) between the leading edge 100 and the trailing edge 102.Each of the root region 96 and the tip region 98 extend from the leadingedge 100 to the trailing edge 102 opposite each other at ends of theairfoil body 90 in the radial direction. That is, the root region 96defines an inner radial end of the airfoil body 90 and the tip regiondefines an outer radial end of the airfoil body 90 (relative to anengine axis).

The airfoil body 90 defines a tip shelf 110, a rib 112, and a tipsquealer pocket 114 formed within the tip region 98 of the airfoil body90.

The tip shelf 110 is radially recessed within the tip region 98 of theairfoil body 90 such that the tip shelf 110 extends toward the rootregion 96. The tip shelf 110 is at least partially disposed between aportion of the rib 112 and the tip squealer pocket 114. The tip shelf110 is disposed between a first wall 120 that at least partially definesthe pressure side 92 of the airfoil body 90 and a second wall 122 thatis disposed between the pressure side 92 and the suction side 94 of theairfoil body 90. The tip shelf 110 extends between the leading edge 100and the trailing edge 102. The tip shelf 110 is spaced apart from theleading edge 100. The tip shelf 110 extends circumferentially betweenthe first wall 120 and the second wall 122. The tip shelf 110 extends inthe axial direction along the tip region 98 of the airfoil body 90.

The tip shelf 110 may be provided with a plurality of cooling holes 111that extend at least partially through the tip shelf 110 and into aninterior of the airfoil body 90.

The rib 112 is radially located within the tip region 98 of the airfoilbody 90 such that the rib 112 is recessed below, radially inward towardthe root section 96, and is radially spaced apart from the tip shelf110. The rib 112 circumferentially extends between the first wall 120and a third wall 124 that at least partially defines the suction side94. The rib 112 extends axially from the trailing edge 102 towards theleading edge 100. The rib 112 is spaced apart from and does notintersect with or contact the leading edge 100.

The rib 112 is spaced apart from and radially inward from the tip shelf110 and a tip surface 126. The tip surface 126 circumferentially extendsbetween the second wall 122 and the third wall 124 at the tip region 98.The tip surface 126 is disposed substantially parallel to but notcoplanar with the tip shelf 110. The tip surface 126 is radially spacedapart from the tip shelf 110.

The rib 112 is disposed in a substantially non-parallel relationshipwith the tip shelf 110 and the tip surface. The rib 112 is disposedcloser to the trailing edge 102 than the leading edge 100. The rib 112is located between the root region 96 and the tip shelf 110. The rib 112is at least partially formed by the first wall 120.

The tip squealer pocket 114 is at least partially defined by the secondwall 122, a third wall 124, and a pocket surface 128 that radiallyextends between the second wall 122 and the third wall 124. The pocketsurface 128 is spaced apart from the tip surface 126. The pocket surface128 is disposed substantially parallel to but not coplanar with the tipsurface 126. The pocket surface 128 is radially spaced apart from thetip shelf 110 and the tip surface 126.

The tip squealer pocket 114 is radially recessed within the tip region98 of the airfoil body 90. The tip squealer pocket 114 is at leastpartially disposed between the suction side 94 and the tip shelf 110.The tip squealer pocket 114 is disposed between the third wall 124 thatat least partially defines the suction side 94 of the airfoil body 90and the second wall 122. The tip squealer pocket 114 extendscircumferentially between the second wall 122 and the third wall 124.The tip squealer pocket 114 extends in a direction from the leading edge100 toward the trailing edge 102. In at least one embodiment, anextension wall 129 circumferentially extends between the second wall 122and the third wall 124. The extension wall 129 radially extends betweenthe root region 96 and the tip region 98.

The tip squealer pocket 114 may be provided with a plurality of coolingholes 115 that extend at least partially through the tip squealer pocket114 into an interior of the airfoil body 90. The tip squealer pocket 114significantly reduces the amount of thermal mass present proximate thetip region 98. The removal of the thermal mass due to the incorporationof the tip squealer pocket 114 will more closely match the transientthermal response of the tip region 98 and of the proximate first,second, and third walls 120, 122, 124. Further, the removal of thermalmass in the tip region 98 will reduce the amount of thermal transientcompressive strain that is incurred during throttle acceleration anddeceleration excursions of the gas turbine engine 20 that occur duringengine operation throughout the aircraft mission flight profile.Furthermore, the removal of thermal mass resulting from theincorporation of the tip squealer pocket 114 will also reduce the localsteady state thermal strain proximate the tip region 98.

Referring to FIGS. 3-6, the airfoil body 90 defines or includes aplurality of interior cavities to enable cooling of the airfoil 60. Forexample, as shown, the airfoil 60 includes a first pressure side hybridskin core cavity 130, a second pressure side hybrid skin core cavity132, a leading edge hybrid skin core cavity 134, a suction side hybridskin core cavity 136, a forward radial flow cavity 138, a tip flagcavity 139, a first serpentine flow cavity 140, a second serpentine flowcavity 142, a third serpentine flow cavity 144, and a trailing edge slot146.

The hybrid skin core cavities are cooling passages or cooling cavitiesthat are disposed immediately adjacent to a hot wall. The hybrid skincore cavities are the resultant hollow cooling passages or cavities thatare created by a solid ceramic core. The solid ceramic core is leachedout of the metal casting airfoil geometry leaving a hollow void orcooling cavity passage that may contain internal heat transferaugmentation features such as trip strips, turbulators, pedestals, pinfins, or the like. The resulting hybrid skin core cavity is positionedimmediately adjacent to and is in close proximity to provide cooling toan external hot wall, e.g. the external wall of the airfoil body 90 suchas an external surface of the first wall 120, the second 122, and thethird wall 124, or an external heat load. The hybrid skin core cavityprovides local cooling to a single hot wall of the airfoil body 90. Assuch, a hybrid skin core cavity may be disposed between or adjacent to ahot wall and a cold wall (e.g. the first pressure side hybrid skin corecavity 130, the second pressure side hybrid skin core cavity 132, theleading edge hybrid skin core cavity 134, the suction side hybrid skincore cavity 136, and the first serpentine flow cavity 140). Conventionalcavities are positioned between and provide cooling to two hot walls(e.g. the second serpentine flow cavity 142 and the third serpentineflow cavity 144). A feed cavity is a cavity that is positioned betweentwo cold walls or walls that are spaced apart from external hot surfacesor walls of the airfoil (e.g. the forward radial flow cavity 138).

Furthermore, the term “skin” refers to an external hot surface or wallof the airfoil (e.g. the first wall 120, the second wall 122, and thethird wall 124). The external hot surface of wall of the airfoil may bearranged close to or proximate an external heat source, i.e. the hot gaspath surface. In this sense the hybrid skin core cavities provide verylocalized convective cooling immediately adjacent to the local hot wallsurface where the hybrid skin core cavity is positioned locally,typically only one airfoil surface (the pressure side 92, the suctionside 94, or the leading edge 100) is influenced by the local convectivecooling provided by the hybrid skin core cavity. In other words, only aone rib roughened wall surface with internal heat transfer augmentationfeatures is providing active convective cooling of the hot wallimmediately adjacent to the hybrid skin core cavity, while withconventional cooling cavity channels typically span across the airfoilfrom the pressure side to the suction side, and provide activeconvective cooling to both the pressure side and the suction sideairfoil surfaces concurrently and have internal heat transferaugmentation features adjacent to both hot wall surfaces. In this sensethese low aspect ratio cooling channels are referred to as “hybrid” skincore cavities.

The term “hybrid” in the context of the present disclosure refers to ahybrid skin core cavities that may contain internal heat transferaugmentation features near or immediately adjacent to a hot wallsurface. The term “hybrid” also refers to providing cooling in localproximity to where the internal heat transfer augmentation feature islocated. The hybrid skin core cavities have a low aspect ratio. In someembodiments, a hybrid skin core cavity may have a height to width ratioof less than about 0.8, while conventional height to width ratios thatare greater than about 0.8. Further, in some embodiments, the leadingedge leading edge hybrid skin core cavity 134 can have a height to widthratio of 0.8 or less. As used with respect to the describe ratio, a“height” of a cavity is a distance from an outer wall of the airfoilthat partially defines the cavity to an inner wall that is internal tothe airfoil (e.g., distance between first wall 120 and the internalpartition wall 176 defining the first pressure side hybrid skin corecavity 130). Further, a width of a cavity is a dimension or length alongone of the walls or surfaces that defines the height dimension.

The low aspect ratio and sizing of the hybrid skin core cavity geometryis typically not conducive to benefiting from the Coriolis effect due toblade rotation. In this sense, the hybrid skin core cavity passagevortices are small and therefore the enhancement of internal convectiveheat transfer attributed to the counter rotating vortices typicallyobserved in larger cooling cavities is not present. In this sense thehybrid skin core cavity geometry is not able to leverage the additionalaugmentation typically observed in conventional cooling cavities.However due to their small cross sectional area, the hybrid skin corecavity geometry is conducive to generating high internal convective heattransfer coefficients due to the high flow per unit area (W/A)achievable with smaller cooling cavities. The hybrid skin core cavitiesmay be formed by a hybrid skin core. A hybrid skin core refers to thephysical core structure that exists after core die injection. The hybridskin core is used to create the final part internal features andrepresents the negative of the final part. The hybrid skin coretypically is made of a silica ceramic or alumina ceramic matrixmaterial. It can also be made from RMC material which is a molybdenumbased core material. The hybrid skin core material is typically in theform of a slurry and then is fired to create a solid ceramic core bodythat is then placed in a wax mold and injected to create the externalairfoil shape, platform, neck, and attachment.

As shown in FIG. 6, the trailing edge slot 146 may be incorporated as anintegral cooling passage comprising one of the legs of the aft flowingserpentine circuit. In this scenario the serpentine design configurationis incorporated with the cooling passages of the trailing edge slot 146that supplies a trailing edge slot configuration that providesconvective cooling at the trailing edge 102 of the airfoil 60. In someembodiments the first, second, and third serpentine flow cavities 140,142, 144 may form a continuous serpentine flow cavity within the airfoil60 that are independent and segregated from any other cooling circuitswithin the airfoil 60. A separate independently fed trailing edge corecavity may be incorporated to supply cooling air to the trailing edgeslot 146.

The configuration of the serpentine flow cavities 140, 142, 144 can takeadvantage of the radially oriented hybrid skin core cavities 130, 132,134, 136 used in high heat load areas of the airfoil. That is, one ormore of the serpentine flow cavities 140, 142, 144 may be positioned andoriented within high heat load areas of the airfoil 60. For example, asdescribed herein and below, a pressure side hybrid skin core cavity 130,132 negates the effects of locally high external heat flux that istypically present along the airfoil pressure side 92. In this instancethe cooling air temperature heat pick up in the serpentine flow cavities140, 142, 144 is mitigated by the shielding provided by the radiallyoriented hybrid skin core cavities 130, 132 adjacent to the first uppass of the first serpentine flow cavity 140. Accordingly, the overallconvective cooling flow requirements may be reduced in the subsequentserpentine cavities 142, 144 due the reduction in cooling airtemperature heat pickup. In some configurations, the airfoil 60 may bepredominantly convectively cooled, thereby enabling the tailoring of thecooling air heat pickup to produce a more isothermal metal temperaturedistribution along the external airfoil pressure side 96, suction side94, airfoil tip 98, leading edge 100, and trailing edge 102 surfaces,resulting in an airfoil cooling design that is more evenly balanced froma durability life perspective. The aft flowing serpentine also enablesthe film cooling flow to be optimally distributed to address airfoil andendwall life limiting locations. In this scenario a limited amount offilm cooling may be required to mitigate locally high external heat fluxand excessive metal temperatures conditions both within and along theairfoil and endwall surfaces. The reduction in both convective and filmcooling flow requirements to achieve durability life goals arebeneficial to both turbine component and stage aerodynamic efficiency.In some embodiments, having an aft flowing serpentine feed the trailingedge 102 of the airfoil 60 may reduce the total airfoil weight byeliminating a rib that would be needed for a dedicated trailing edgecooling cavity.

The first pressure side hybrid skin core cavity 130 and the secondpressure side hybrid skin core cavity 132 extend radially from the rootregion 96 of the airfoil body 90 toward the tip region 98 and arelocated proximate the leading edge 100 and proximate the pressure side92. The first pressure side hybrid skin core cavity 130 and the secondpressure side hybrid skin core cavity 132 are spaced apart from eachother proximate the tip region 98 (e.g., spaced axially apart along thepressure side 92). In at least one embodiment, the first pressure sidehybrid skin core cavity 130 and the second pressure side hybrid skincore cavity 132 are joined together proximate the root region 96 and areprovided with cooling air from a pressure side inlet cavity.

The first pressure side hybrid skin core cavity 130 and the secondpressure side hybrid skin core cavity 132 are at least partially formedwithin the interior of the airfoil 60 and proximate the first wall 120.At the tip region 98, the first pressure side hybrid skin core cavity130 and the second pressure side hybrid skin core cavity 132 each extendthrough the tip shelf 110 thus enabling fluid communication from theroot region 96 to the tip region 98 through the interior of the airfoil60.

The first pressure side hybrid skin core cavity 130 and the secondpressure side skin core cavity 132 may have unique geometric shapes withvarying cross sectional area as a function of radial and axial locationwithin airfoil 60. In some instances it is desirable to taper theinternal cooling cavity geometry in the radial direction as shown inFIGS. 5 and 6. The cooling air passages are geometrically tapered in theradial flowing cavities as the coolant flow enters the root region 96and progresses toward the tip region 98. The predominantly radiallyflowing pressure side hybrid skin core cavities 130, 132 are designed tohave constant and/or converging cavity flow areas. The taper in cavityareas are desirable from a thermal convective cooling perspective inthat it allows for the tailoring of internal heat transfer augmentationfeatures, such as turbulators, trip strips, pin fins, pedestals etc. Inthis scenario both the internal cavity pressure loss, convective heattransfer, and cooling air temperature can be tailored to thermally matchthe local radial and axial external heat flux distribution along thepressure side 92.

The first pressure side hybrid skin core cavity 130 and the secondpressure side hybrid skin core cavity 132 receive cooling air from apressure side inlet cavity that is disposed proximate the root region96. The first pressure side hybrid skin core cavity 130 and the secondpressure side hybrid skin core cavity 132 are configured to providecooling to the tip shelf 110. Cooling air may be supplied from the rootregion 96 (e.g., from the pressure side inlet cavity), flow in a radialdirection through the first and second pressure side hybrid skin corecavities 130, 132, and out at the tip region 98 and particularly at thetip shelf 110. In some configurations, the cooling may be slot filmcooling, as shown FIG. 4 and FIG. 5.

The slot film cooling provided by the first pressure side hybrid skincore cavity 130 and the second pressure side hybrid skin core cavity 132minimizes the potential of hot gas entrainment that may occur as aresult of local vortices created at the tip region 98 of the airfoil 60.The continuous sheet of film cooling air that exits the first pressureside hybrid skin core cavity 130 and the second pressure side hybridskin core cavity 132 at the tip shelf 110 mitigates the propensity ofhot gas entrainment along the tip shelf 110 and the second wall 122 ofthe tip region 98. The slot film discharge flow from the first pressureside hybrid skin core cavity 130 and the second pressure side hybridskin core cavity 132 is extremely effective in providing an insulatinglayer of film coolant due to the reduction in the strength ofcounter-rotating film vortices associated with slot geometry shapes andthe orientation of the slot cavity exit geometry (e.g., slot geometry)of the first pressure side hybrid skin core cavity 130 and the secondpressure side hybrid skin core cavity 132, relative to the local airfoiltip region 98 streamlines.

The exit slots of the first pressure side hybrid skin core cavity 130and the second pressure side hybrid skin core cavity 132 are locatedadjacent to the radial extending (vertical) surface of the second wall122 that in part defines the tip shelf 110 and are coincident with theexposed surface of the second wall 122. The location of the slot exitsof the first pressure side hybrid skin core cavity 130 and the secondpressure side hybrid skin core cavity 132 at the tip shelf 110 areselected to ensure that the film cooling air is ejected along theradially extended surface and remains attached to the radially extending(vertical) second wall 122. The cooling air is expelled in apredominately radial orientation and is then diffused and expandedcircumferentially and axially in the leeward direction toward thehorizontal surface of the tip shelf 110 of the airfoil 60 proximate thetip region 98 and ultimately toward the suction side 94 proximate thetrailing edge 102. The diffusion of the film cooling hole geometry inthe leeward direction enables the cooling air flow to be discharged in adirection of favorable pressure gradient across the horizontal tipsurface of the airfoil 60 proximate the tip region 98.

Referring to FIGS. 7-9 and 11, the first pressure side hybrid skin corecavity 130 and the second pressure side hybrid skin core cavity 132 aswell as the pressure side inlet cavity may be formed by a pressure sidehybrid skin core 150. The pressure side hybrid skin core 150 may be usedduring a manufacturing process to form the airfoil 60 having the abovedescribed cavities (e.g., first and second pressure side hybrid skincore cavities 130, 132). In accordance with some embodiments, themanufacturing process is an investment casting process, althoughalternative manufacturing techniques, including advanced additivemanufacturing processes, may be utilized to fabricate ceramic silica oralumina core bodies and/or directly additively manufacture airfoilgeometries using nickel based powders to produce airfoil internalcooling geometries and design configurations in accordance withembodiments of the present disclosure.

Referring to FIG. 11, the pressure side hybrid skin core 150 includes afirst trunk 152, a first branch 154, and a second branch 156. The firsttrunk 152 extends toward the tip region 98. The first trunk 152 isconfigured to form or define at least a portion of the pressure sideinlet cavity. The first branch 154 and the second branch 156 extend froman end of the first trunk 152 toward the tip shelf 110 of the tip region98. The first branch 154 is configured to form or define the firstpressure side hybrid skin core cavity 130. The second branch 156 isconfigured to form or define the second pressure side hybrid skin corecavity 132.

The first branch 154 has a first profile and the second branch 156 has asecond profile. In some embodiments, the first profile and the secondprofile have different core profile shapes and/or form different coolingcavity geometries as it pertains to the aspect ratio of the channel,e.g. the height and width (H/W). That is, in some embodiments, thesecond profile can have a geometric cavity shape that is different fromthe first profile geometric cavity shape. In such configurations, thefirst branch 154 may have a first width, w1 (in the axial direction)proximate a distal end disposed opposite a proximal end to the firsttrunk 152 and the second branch 156 has a second width, w2, (in theaxial direction) proximate the distal end disposed opposite a proximalend to the first trunk 152. In some embodiments, the second width, w2,is greater than the first width, w1. In some embodiments, the secondpressure side hybrid skin core cavity 132 may have a larger or longerexit opening in the tip shelf 110 than the first pressure side hybridskin core cavity 130. That is a width of the second pressure side hybridskin core cavity 132 at the tip region 98 may be, in some embodiments,larger than a width of the first pressure side hybrid skin core cavity130 at the tip region 98. Conversely in some embodiments the first widthw1 may be larger than the second width w2. The geometry shape and sizerequirements are defined based on the cooling flow available and theexternal heat load distribution and thermal cooling effectivenessrequirements needed to meet airfoil durability metal temperature andlife requirements.

Similarly the cavity or channel height of the first pressure side hybridskin core cavity 130 may be different than the cavity or channel heightof the second pressure side hybrid skin core cavity 132. Additionallythe pressure side hybrid skin core cavities 130, 132 cavity channelshapes may also be unique and consist of varying degrees of curvaturefor the internal cavity surface immediately adjacent to the externalwall of the pressure side 92. Likewise the opposite wall surfaceimmediately adjacent to an internal partition wall 176 of the first andsecond pressure side hybrid skin core cavities 130, 132 may alsocomprise of a unique curvature different than the first wall surfaceimmediately adjacent to the external wall of the pressure side 92. Inthis manner the radial cavity Reynolds Number, Mach Number, internalconvective heat transfer, pressure loss, and coolant temperature heatpick up can be uniquely optimized to better balance differences in thelocal heat flux distribution along the external airfoil pressure side92.

In some embodiments, the pressure side hybrid skin core 150 may beprovided with features that may form or define internal convective heattransfer augmentation features within the pressure side inlet cavity,the first pressure side hybrid skin core cavity 130, and/or the secondpressure side hybrid skin core cavity 132. The internal convective heattransfer augmentation features may be, for example, trip strips,turbulators, pin fins, and/or pedestals that enable enhanced thermalcooling effectiveness levels to be achieved.

Referring back to FIGS. 3-6, the leading edge hybrid skin core cavity134 extends from the root region 96 towards the tip region 98 of theairfoil body 90. The leading edge hybrid skin core cavity 134 is locatedproximate the leading edge 100 of the airfoil body 90. The leading edgehybrid skin core cavity 134 is axially and circumferentially spacedapart from the first pressure side hybrid skin core cavity 130. Theleading edge hybrid skin core cavity 134 is axially spaced apart fromthe leading edge 100. The extension wall 129 is disposed between thefirst pressure side hybrid skin core cavity 130 and the leading edgehybrid skin core cavity 134.

In some embodiments, as shown in FIGS. 5-6, the leading edge hybrid skincore cavity 134 has an arcuate shape, contour, and/or geometry thatfollows or matches the local shape, contour, and/or curvature of thelocal external leading edge aerodynamic geometry of the surface of theleading edge 100. In other embodiments, the leading edge hybrid skincore cavity 134 may be formed having a shape, contour, and/or geometrythat is different from the shape, contour, and/or geometry of theleading edge. The geometric attributes of the leading edge hybrid skincore cavity 134 can be modified as described previously for the firstand second pressure side hybrid skin core cavities 130, 132. Similarly,the radial cavity Reynolds Number, Mach Number, internal convective heattransfer, pressure loss, and coolant temperature heat pick up can beuniquely optimized to better balance differences in the local heat fluxdistribution along the external surface of the leading edge 100.

The leading edge hybrid skin core cavity 134 is at least partiallydefined within a portion of the third wall 124 that extends from or isdisposed proximate the leading edge 100. The leading edge hybrid skincore cavity 134 receives cooling air from a leading edge inlet cavitythat is disposed proximate the root region 96. The leading edge hybridskin core cavity 134 is configured to provide cooling flow within tipsquealer pocket 114. Cooling air may be supplied from the root region 96(e.g., from the leading edge inlet cavity), flow in a radial directionthrough the leading hybrid skin core cavity 134, and out at the tipregion 98 and particularly within the leading edge portion of the tipsquealer pocket 114. In some configurations, the cooling may be slotfilm cooling, as shown FIG. 4 and FIG. 5.

The leading edge hybrid skin core cavity 134 opens from the interior ofthe airfoil body 90 and is discharged into the recessed portion of thetip squealer pocket 114, as shown in FIGS. 4-5. Cooling air flowingthrough the leading edge hybrid skin core cavity 134 exits into theleading edge portion of the tip squealer pocket 114 immediately adjacentto the first wall 120 located proximate the leading edge 100.

The leading edge hybrid skin core cavity 134 receives cooling air from aleading edge inlet cavity that is located proximate the root region 96.The leading edge hybrid skin core cavity 134 is fluidly connected to theleading edge inlet cavity. The leading edge hybrid skin core cavity 134is configured to provide tip cooling film to the leading edge portion ofthe tip squealer pocket 114. The film cooling air that exits through theslot of the leading edge hybrid skin core cavity 134 attaches (or flowsacross) to the third wall 124. The location of the slot exit of theleading edge hybrid skin core 134 is positioned immediately adjacent,coincident, and tangent to the leading edge portion of the third wall124 to ensure that the film cooling air is ejected along the radiallyextended surface and stays attached to the leading edge portion of thethird wall 124. The cooling air is expelled in a predominately radialorientation in the leading edge portion of the tip squealer pocket 114.The film cooling from the exit slot of the leading hybrid skin core 134then migrates over the horizontal surface of the leading edge portion ofthe third wall 124 of the airfoil 60 proximate the tip region 98 andultimately toward the suction side airfoil surface 94.

Additionally, as the film cooling air is expelled in a predominatelyradial orientation out of the slot exit of the leading edge hybrid skincore 134 into the tip squealer pocket 114 it enables the cooling air tobe discharged in a direction of favorable pressure gradient across thetip squealer pocket 114. A portion of the cooling air that exits throughthe leading edge hybrid skin core cavity 134 is dispersed into theplenum of the cavity of the tip squealer pocket 114, resulting in somediffusion of the tip slot cooling flow. The dispersion of the slot exitflow provides a buffer of insulating air between hot external gasstreams and the third wall 124 in order to maintain a minimal gapclearance between the tip region 98 of the airfoil 60 and the bladeouter air seal 82 for optimal turbine performance and efficiency. Thecooling air ensures that the metal temperature proximate the tipsquealer pocket 114 remains uniformly cooled in order to minimize localcompressive strain induced by locally high thermal temperature gradientinduced by non-uniformities in thermal cooling performance and transientmetal temperature response rates incurred during engine operation. Itwill be appreciated that any or all cavities with exits proximate thetip of the airfoil may be positioned such that the exiting air exitsinto a pocket or along the tip surface immediately adjacent one or morewalls or surfaces. Further, in some embodiments, the exits of thecavities described herein at the tip of the airfoil may be recessed fromthe actual physical tip of the airfoil (e.g., as shown in FIGS. 3-4).That is, the air exiting one or more of the cavities may not be alongthe tip surface 126, but rather may be radially inward therefrom (e.g.,within a pocket). Such positioned exiting of air may be configured suchthat it does not interfere with or impact an abrading surface of theairfoil (e.g., a tip surface that interacts with a BOAS). However, inother embodiments, the exiting air, and thus the position of the exits,may be arranged to exit direction at, on, or along the tip surface 126.

Referring to FIGS. 7-9 and 12, the leading edge hybrid skin core cavity134 is formed by a leading edge hybrid skin core 160. The leading edgehybrid skin core 160 may be used during a manufacturing process to formthe leading edge hybrid skin core cavity 134 within an airfoil body 90.In accordance with some embodiments, the manufacturing process is aninvestment casting process, although alternative manufacturingtechniques, including advanced additive manufacturing processes, may beutilized to fabricate ceramic silica or alumina core bodies and/ordirectly additively manufacture airfoil geometries using nickel basedpowders to produce form blade airfoil internal cooling geometries anddesign configurations in accordance with embodiments of the presentdisclosure.

The leading edge hybrid skin core 160 is circumferentially and axiallyspaced apart from the pressure side hybrid skin core 150 when positionedto form an airfoil (e.g., as shown in FIGS. 7-9). The leading edgehybrid skin core 160 extends from the root region 96 toward the tipregion 98. In some embodiments, and noted above, the leading edge hybridskin core 160 may have a geometry profile that is uniformly offset andfollows or mimics the external leading edge profile of the leading edge100 of the airfoil body 90. The geometric shape of the leading edgehybrid skin core 160 may also be unique and consist of varying degreesof surface curvature in order to optimize the external wall thicknessdistribution adjacent to the leading edge 100. Likewise the oppositewall surface immediately adjacent to the internal partition wall 176 ofthe leading edge hybrid skin core cavity 134 may also comprise of aunique curvature different than the first wall surface immediatelyadjacent to the external wall of the leading edge 100. In this mannerthe radial cavity Reynolds Number, Mach Number, internal convective heattransfer, pressure loss, and coolant temperature heat pick up can beuniquely optimized to better balance differences in the local heat fluxdistribution along the external airfoil leading edge 100. A portion ofthe leading edge hybrid skin core 160 is disposed generally parallel tothe first trunk 152 of the pressure side hybrid skin core 150. As shownin FIGS. 5 and 7-8, a portion of the leading edge hybrid skin core 160that is disposed proximate the tip region 98 has a complementary profilerelative to the profile of the first branch 154 of the pressure sidehybrid skin core 150.

In some embodiments, the leading edge hybrid skin core 160 may includevarious types of geometric features that generate and promote near wallflow vorticities of the internal cooling air in order to augment localconvective heat transfer. The internal convective heat transferaugmentation features may be located within the leading edge hybrid skincore 160 and/or the leading edge hybrid skin core cavity 134. Theinternal convective heat transfer augmentation features such as tripstrips, turbulators, pin fins, and/or pedestals enable an increase inthe local leading edge thermal cooling effectiveness.

Referring to FIG. 6, backside impingement cooling hole features may beincorporated between the forward radial flow cavity 138 and the leadingedge hybrid skin core cavity 134. Accordingly, in some embodiments, asignificant increase in the backside convective heat transfercoefficient can be achieved. The low aspect ratio geometry of theleading edge hybrid skin core cavity 134 significantly reduces theimpingement distance and places the impingement jets emanating from theforward radial flow cavity 138 in close proximity to the backside of theinternal leading edge wall surface of the leading edge hybrid skin corecavity 134 immediately adjacent to the leading edge 100. The quantity,size, and shape of the impingement geometries may be circular,elliptical, oblong, tear drop, or any multifaceted geometric designconfigurations. Additionally the leading edge impingement holes may beof a singular row, as shown in FIG. 6, and may be either aligned and/oroffset relative to each adjacent impingement cooling hole designfeatures. In some configurations the leading edge impingement array mayconstitute of at least one singular row, or multiple rows distributedcircumferentially along the internal partition wall 176. The leadingedge impingement holes may be aligned, staggered, and/or of varyingradial and circumferential pitch distributions, size, and shapedependent on geometric, heat load, cooling flow, and the leading edge100 thermal cooling effectiveness and durability metal temperature liferequirements.

In some embodiments showerhead film cooling holes may be incorporated inconjunction with a leading edge impingement cooling design and theinternal convective heat transfer at the entrance or inlet of theleading edge showerhead film cooling holes will be further enhanced. Theadditional internal convective heat transfer augmentation at theentrance of the leading edge showerhead film cooling holes are a resultof the increased vorticity and turbulent mixing of the coolant flowproduced by the upstream impingement cooling jets. The net effectassociated with the augmentation of the internal backside impingementheat transfer and the enhancement of convective heat transfer at theinlet of the leading edge film cooling holes further increases thethermal cooling effectiveness and durability capability along theleading edge 100.

The leading edge hybrid skin core 160 enables the reduction in localleading edge external wall thickness requirements adjacent to theleading edge 100. The significantly larger aerodynamic leading edgediameter enables the shape, curvature, and contour of the leading edgehybrid skin core cavity 134 to more closely match the adjacent externalleading edge airfoil geometry 100.

Conversely conventional airfoil aerodynamic geometries are not conduciveto the implementation of a leading edge hybrid skin core cavity 134 thatmay result in a thinner local leading edge external wall thickness.Therefore such leading edge cooling cavity geometries, whether forradial flow and/or impingement leading edge cooling configurations, havelocal leading edge external walls that are significantly thicker bycomparison. The increased leading edge wall thickness is driven by boththe aerodynamic leading edge airfoil geometry 100 and the minimum coregeometry size limitations associated with core die manufacturing, coreproducibility and casting process constraints, as well as the necessityto absorb impact from particulate matter present in the freestreamduring engine operation.

In accordance with embodiments of the present disclosure, the externalwall thickness along the leading edge 100 is reduced but the localthermal performance of the leading edge 100 will not be compromised as aresult of a puncture or other foreign or domestic object damage. Thepressure of the coolant air within the leading edge hybrid skin corecavity 134 is greater than the local external gas path pressure,ensuring that a positive out flow condition will always exist.

The leading edge hybrid skin core cavity 134 is in close proximity tothe leading edge 100 and immediately adjacent to high external heat fluxlocation along the stagnation region proximate the leading edge 100 ofthe airfoil 60. The reduction in local leading edge wall thicknesscombined with the high internal convective heat transfer achievable withthe leading edge hybrid skin core cavity 134 results in a significantincrease in the local thermal cooling effectiveness. Consequently theimproved heat transfer characteristics of the leading edge designconfiguration results in cooler operating metal temperatures andincreased durability capability at similar and/or reduced cooling flowrates relative to conventional leading edge cooling designconfigurations.

The thinner external leading edge wall thickness also reduces the weightof the airfoil 60 and subsequent airfoil blade pull on the rotating diskattachment and rotor. The increase in local leading edge thermal coolingeffectiveness achievable in accordance with the embodiments of thepresent disclosure will significantly reduce the amount of coolingairflow necessary to achieve turbine airfoil metal temperature anddurability life requirements. The reduction in cooling flow requirementsdirectly translates into increased turbine stage and thermodynamic cycleefficiency which directly improves the Total Specific Fuel Consumption(TSFC) of the overall propulsion system.

Referring back to FIGS. 3-6, the suction side hybrid skin core cavity136 extends from the root region 96 towards the tip region 98 of theairfoil body 90. The suction side hybrid skin core cavity 136 is locatedproximate the suction side 94 of the airfoil body 90. The suction sidehybrid skin core cavity 136 is spaced apart from the leading edge hybridskin core cavity 134. The first pressure side hybrid skin core cavity130, the second pressure side hybrid skin core cavity 132, the leadingedge hybrid skin core cavity 134, and the suction side hybrid skin corecavity 136 are arranged immediately adjacent about a perimeter of theforward radial flow cavity 138 in order to form a shielding arrangementas shown in FIGS. 6, 17, and 18. The shielding arrangement thermallyprotects and insulates the forward radial flow cavity 138 from the highexternal heat flux present immediately along the pressure side 92, theleading edge 100, and the suction side 94.

The shielding arrangement of the radially oriented hybrid skin cavities130, 132, 134, 136 significantly reduces the coolant air temperatureheat pick up that occurs in the forward radial flow cavity 138. In thisinstance the cooling air temperature increase in the forward radial flowcavity 138 is predominately a function of solid body pumping induced bythe inertial forces generated by the rotating airfoil only. Whereas theair temperature increase in the cooling cavities immediately adjacent tothe hot external airfoil wall surfaces (e.g., cavities 130, 132, 134,136) incur a higher rate of cooling air temperature increase, which is aresult of both solid body pumping induced by the inertial forcesgenerated by the rotating airfoil, as well as, the heat addition due tothe energy transfer of heat from the hotter external airfoil wallsconvecting into the cooler working fluid within the radially flowinghybrid skin core cavities 130, 132, 134, 136.

The absolute temperature of the cooling air in the forward radial flowcavity 138 will be significantly lower as it enters the tip flag cavity139. The increase in temperature gradient between the hot freestreamexternal gas and the internal working cooling fluid provides for a moreefficient use of the available cooling air flow to achieve the desiredairfoil operating metal temperature conditions necessary to meetdurability life requirements. The cooling air temperature rise will besignificantly greater in the radially oriented skin core cavitiesforming the shielding arrangement, e.g. the first pressure side hybridskin core cavity 130, the second pressure side hybrid skin core cavity132, the leading edge hybrid skin core cavity 134, the suction sidehybrid skin core cavity 136. As shown in FIG. 6, the cavities within theairfoil 60, that form the first serpentine flow cavity 140, the secondserpentine flow cavity 142, and the third serpentine flow cavity 144,will also observe a decrease in the cooling air heat pick up due to thethermal shielding provided by the second pressure side hybrid skin corecavity 132. The decrease in cooling air heat pick up in the serpentinepassages results in lower local hot wall metal temperatures andincreased durability life capability. The reduction in cooling airtemperature heat pick up due to the thermal shielding provided by thepressure side hybrid skin core cavity 132 enables the cooling air flowrequirements for the serpentine circuit to be reduced while maintaininglocal metal temperatures consistent with an unshielded serpentinecooling design configuration at constant durability life. The reductionin serpentine cooling flow requirements directly translates intoincreased turbine stage and thermodynamic cycle efficiency whichdirectly improves the Total Specific Fuel Consumption (TSFC) of theoverall propulsion system.

The tip exit slot formed by the suction side hybrid skin core cavity 136is at least partially defined within a portion of the third wall 124, asshown in FIGS. 3 and 4. The location of the suction side hybrid skincore cavity 136 opens from the interior of the airfoil body 90 and isdischarged into the recessed portion of the tip squealer pocket 114, asshown in FIGS. 4-5. The suction side hybrid skin core cavity 136 isconfigured to provide cooling flow within tip squealer pocket 114.Cooling air may be supplied from the root region 96 (e.g., from thesuction side hybrid inlet cavity), and flows in a radial directionthrough the suction side hybrid skin core cavity 136, and out at the tipregion 98 and particularly within the suction side portion of the tipsquealer pocket 114. In some configurations, the cooling may be slotfilm cooling, as shown FIG. 4 and FIG. 5.

The suction side hybrid skin core cavity 136 exits into the tip squealerpocket 114 and is located immediately adjacent, coincident, and tangentto the suction side portion of the third wall 124 in order to ensurethat the slot film cooling air is ejected along the radially extendedsurface and stays attached to the suction side portion of the third wall124. The cooling air is expelled in a predominately radial orientationalong the suction side region of the tip squealer pocket 114. The filmcooling from the exit slot of the suction side hybrid skin core 136 isthen partially diffused into the recessed portion of the tip squealerpocket 114 and then migrates over the horizontal surface of the suctionside portion of the third wall 124 of the airfoil 60 proximate the tipregion 98 and ultimately toward the suction side 94.

Referring to FIG. 9, the suction side hybrid skin core cavity 136receives cooling air from a suction side inlet cavity that is disposedproximate the root region 96. The suction side hybrid skin core cavity136 is configured to provide tip cooling film into the tip squealerpocket 114. The cooling air that exits through the suction side hybridskin core cavity 136 attaches to the third wall 124. The cooling airthat exits through the suction side hybrid skin core cavity 136 isexpelled in a predominately radial orientation and enables the coolingair to be discharged in a direction of favorable pressure gradientacross the tip squealer pocket 114. The cooling air that exits throughthe suction side hybrid skin core cavity 136 provides a buffer ofinsulating air between hot external gas streams and the third wall 124in order to maintain a minimal gap clearance between the tip region 98and the blade outer air seal 82 for optimal turbine performance andefficiency. The film cooling air ejected into the recessed portion ofthe tip squealer pocket 114 and the surrounding radially extendingexternal airfoil walls 122, 124 proximate the leading edge 100 ensuresthat the metal temperature proximate the tip squealer pocket 114 remainsuniformly cooled in order to minimize local compressive strain inducedby locally high thermal temperature gradient induced by non-uniformitiesin thermal cooling performance and transient metal temperature responserates incurred during engine operation.

Referring to FIGS. 7-10, the suction side hybrid skin core cavity 136 isformed by a suction side hybrid skin core 170. The suction side hybridskin core 170 may be used during a manufacturing process to form theleading edge hybrid skin core cavity 134 within an airfoil body 90. Inaccordance with some embodiments, the manufacturing process is aninvestment casting process, although other manufacturing techniques,including advanced additive manufacturing processes, may be utilized tofabricate ceramic silica or alumina core bodies and/or directlyadditively manufacture airfoil geometries using nickel based powders toproduce form blade airfoil internal cooling geometries and designconfigurations.

The suction side hybrid skin core 170 is spaced apart from the leadingedge hybrid skin core 160. The suction side hybrid skin core 170 extendsfrom the root region 96 toward the tip region 98. In some embodiments,the suction side hybrid skin core 170 may have a width that varies alongthe radial length of the suction side hybrid skin core 170, e.g.,forming a variable width cavity between the tip squealer pocket 114 andthe suction side inlet cavity. For example, the suction side hybrid skincore 170 may be formed with a first width, w1, at an end proximate theroot region 96, a second width w2 at an end proximate the tip region 98,and a third width w3 located between the root region 96 and the tipregion 98. In some embodiments, the first width w1 is greater than thesecond width w2. Further, in some embodiment, the first width w1 isgreater than the third width w3. In still further embodiments, the thirdwidth w3 is less than the first width w1 and the second width w2. Thoseof skill in the art will appreciate that these relative widths of thefirst, second, and third widths of the suction side hybrid skin core 170are for example and various other width relationships may be employedwithout departing from the scope of the present disclosure. For example,in various embodiments, the above described first, second, and thirdwidths can be similarly applied to the other hybrid skin cores describedherein (e.g., hybrid skin cores 150, 160, etc.).

Additionally the cavity or channel height of the suction side hybridskin core cavity 136 may also be of varying channel heights in thepredominately stream-wise radial direction of the internal cavitycooling flow. Further, the shape of the suction side hybrid skin corecavity 136 may also be unique and consist of varying degrees ofcurvature for the internal cavity surface immediately adjacent to theexternal wall of the suction side 94. Likewise the opposite wall surfaceimmediately adjacent to the internal partition wall 176 of the suctionside hybrid skin core cavity 136 may also comprise of a unique curvaturedifferent than the first wall surface immediately adjacent to theexternal wall of the suction side 94. In this manner the radial cavityReynolds Number, Mach Number, internal convective heat transfer,pressure loss, and coolant temperature heat pick up can be uniquelyoptimized to better balance differences in the local heat fluxdistribution along the external surface of the suction side 94.

The suction side hybrid skin core 170 may be provided with features thatmay form or define internal convective heat transfer augmentationfeatures within the suction side inlet cavity and/or the suction sidehybrid skin core cavity 136. The internal convective heat transferaugmentation features may be, for example, trip strips, turbulators, pinfins, and/or pedestals that enable enhanced thermal coolingeffectiveness levels to be achieved.

The forward radial flow cavity 138 extends from the root region 96towards the tip region 98 of the airfoil body 90. The forward radialflow cavity 138 is radially recessed inboard with respect to the pocketsurface 128 within the tip squealer pocket 114. The forward radial flowcavity 138 is located between the leading edge hybrid skin core cavity134 and the first serpentine flow cavity 140. The forward radial flowcavity 138 is located between the first pressure side hybrid skin corecavity 130 and the suction side hybrid skin core cavity 136.

In some embodiments, the forward radial flow cavity 138 is formed withsmooth internal walls that do not contain internal convective features,although in some embodiments such features may be provided. The forwardradial flow cavity 138 receives cooling air from a forward radial flowinlet cavity that is located proximate the root region 96. The forwardradial flow cavity 138 provides a tip cooling film at significantlyreduced temperatures compared to the cooling film that exits from thefirst pressure side hybrid skin core cavity 130, the second pressureside hybrid skin core cavity 132, the leading edge hybrid skin corecavity 134, and/or the suction side hybrid skin core cavity 136. Heatpickup of the cooling air that flows through the forward radial flowcavity 138 is predominantly driven by solid body pumping induced by theinertial forces generated by the rotation of the airfoil 60. Thereduction in cooling air temperature within the forward radial flowcavity 138 creates a larger temperature difference as it enters theaxial tip flag cavity 139. The increase in temperature gradient betweenthe hot freestream external gas and the internal working cooling fluidprovides for a more efficient use of the available cooling air flow toachieve the desired airfoil operating metal temperature conditionsnecessary to meet durability life requirements.

Referring to FIG. 6, the forward radial flow cavity 138 is optionallyfluidly connected to the leading edge hybrid skin core cavity 134 by oneor more resupply openings 174 A,B. The impingement resupply openings 174A,B extend through the internal partition wall 176 that is located orpositioned between and separates the forward radial flow cavity 138 andthe leading edge hybrid skin core cavity 134. In some embodiments, asingle resupply opening may extend through the internal partition wall176. The internal partition wall 176 and the first wall 120 at leastpartially define the first pressure side hybrid skin core cavity 130 andthe second pressure side hybrid skin core cavity 132. The internalpartition wall 176 and the third wall 124 at least partially define theleading edge cavity 134. The internal partition wall 176 and the thirdwall 124 at least partially define the suction side hybrid skin corecavity 136. Segments of the internal partition wall 176 at leastpartially define the radial flow cavity 138. Further, in someembodiments, the internal partition wall 176 can extend within and/orthrough the airfoil beyond what is shown in FIG. 6. Additionally,multiple internal partition walls can be formed within the airfoil toform multiple feed cavities. Further, example, an internal partitionwall can extend adjacent into and/or to the serpentine cavities, feedcavities, hybrid skin core cavities, conventional cavities, etc. In onenon-limiting example, the presently shown internal partition wall 176can extend toward the trailing edge 102 into the second serpentine flowcavity 142, and in some embodiments, may divide the second serpentineflow cavity 142 into two hybrid skin core cavities (in comparison to aconventional cavity as presently shown in FIG. 6. Similarly, in someembodiments, the presently shown internal partition wall 176 can extendtoward the trailing edge 102 into the first serpentine flow cavity 140on the suction side 94 (e.g., adjacent the third wall 124) to form anadditional hybrid skin core cavities on the suction side 94 and furtherform a feed cavity between this additional suction side hybrid skin corecavity and the second pressure side hybrid skin core cavity 132. Thoseof skill in the art will appreciate that the internal partition wall 176can form various walls or structures to define one or more cavities ofvarying type (e.g., hybrid skin core cavity, feed cavity, conventionalcavity).

The internal partition wall 176 separates the first pressure side hybridskin core cavity 130, the leading edge cavity 134, the suction sidehybrid skin core cavity 136, and the first serpentine flow cavity 140from the radial flow cavity 138, such that the internal partition wall176 is disposed or extends about the radial flow cavity 138. Theinternal partition wall 176 is disposed between and separates the firstpressure side hybrid skin core cavity 130 from the second pressure sidehybrid skin core cavity 132. The internal partition wall 176 is disposedbetween and separates the suction side hybrid skin core cavity 136 fromthe first serpentine flow cavity 140. The impingement resupply openings174 A,B can be formed by one or more structures that connect or extendbetween the leading edge hybrid skin core 160 and the radial core 182,as will be appreciated by those of skill in the art. That is, whenforming an airfoil in accordance with an embodiment of the presentdisclosure, the leading edge hybrid skin core 160 and the radial core182 can be configured with structures extending therebetween to form theimpingement resupply openings 174 A,B that connect the forward radialflow cavity 138 and the leading edge hybrid skin core cavity 134 in theformed airfoil body 90.

The impingement resupply openings 174 A,B enable both high pressure andlower temperature cooling air from the forward radial flow cavity 138 toflow into the leading edge hybrid skin core cavity 134. The higherpressure and colder cooling air supplied by the forward radial flowcavity 138 may be required to mitigate increased internal cavity totalpressure losses and cooling air temperature heat pickup attributed tothe high thermal convective efficiency characteristics achievable withinthe leading edge hybrid skin core cavity 134. The impingement resupplyopenings 174 A,B may be implemented to enable more distributed fluidcommunication between the forward radial flow cavity 138 and the leadingedge hybrid skin core cavity 134. Incorporating two or more dispersedarrays of impingement resupply openings 174 A,B will provide a moreuniform circumferential and radial distribution of backside convectiveheat transfer and thermal cooling effectiveness along the internal wallsurface of at least one of the leading edge hybrid skin core cavity 134and the forward radial flow cavity 138. A generally uniform distributionof resupply air through the resupply openings 174 mitigatescircumferential and radial thermal metal temperature gradients,therefore reducing local temperature gradients circumferentially andradially along the leading edge 100 and thereby reducing the localthermal mechanical strain.

The impingement resupply openings 174 A,B may be incorporated inconjunction with film cooling holes 178. The film cooling holes 178 mayextend at least partially through the third wall 124 proximate theleading edge 100. In some embodiments, a single film cooling hole may beprovided proximate the leading edge 100. In some embodiments,centerlines of the film cooling holes 178 and the impingement resupplyopenings 174 A,B may be proximately aligned. In other embodiments,centerlines of the film cooling holes 178 and the impingement resupplyopenings 174 A,B may be circumferentially offset from each other suchthat their respective centerlines are not proximately aligned.

The internal partition wall 176 separates the forward radial flow cavity138 from the first pressure side hybrid skin core cavity 130, theleading edge hybrid skin core cavity 134, and the suction side hybridskin core cavity 136. The internal partition wall 176 radially extendsbetween the root region 96 and the tip region 98. The internal partitionwall 176 is circumferentially disposed about the forward radial flowcavity 138.

Although shown herein with film cooling holes and impingement holeslocated in certain or specific areas, such placement is not to belimiting. For example, in other embodiments various fluid connectingholes can be provided to fluidly connect one or more (e.g., any) of thecavities of the airfoil (hybrid, conventional, or feed). That is, forexample, first pressure side hybrid skin core cavity 130, a secondpressure side hybrid skin core cavity 132 can be fluidly connected byone or more cross-over holes or apertures. Similarly, cross-overs can beformed between different sections of the serpentine cavity (e.g.,up-pass and down-pass can be fluidly connected through cross-overapertures). In another example, one or both of the first pressure sidehybrid skin core cavity 130 and the suction side hybrid skin core cavity136 may include fluid connection apertures to fluidly connect with theforward radial flow cavity 138. Further, in another example, the leadingedge hybrid skin core cavity 134 can be fluidly connected to one or more(e.g., either or both) pressure/suction cavities (e.g., the suction sidehybrid skin core cavity 136, first pressure side hybrid skin core cavity130, second pressure side hybrid skin core cavity 132). Those of skillin the art will appreciate that the hybrid skin cores used to form thehybrid skin core cavities can be manufactured and/or assembled withstructures appropriate to form the fluid connections between cavities.

Referring to FIGS. 7-10, 13-16, and 18, the forward radial flow cavity138 is formed by a portion of a forward radial flow core 180. Theforward radial flow core 180 may be used during a manufacturing processto form the forward radial flow cavity 138 within the airfoil body 90.In accordance with some embodiments, the manufacturing process is aninvestment casting process, although other manufacturing techniques,including advanced additive manufacturing processes, may be utilized tofabricate ceramic silica or alumina core bodies and/or directlyadditively manufacture airfoil geometries using nickel based powders toproduce form blade airfoil internal cooling geometries and designconfigurations to form blades and airfoils in accordance withembodiments of the present disclosure.

The forward radial flow core 180, as shown, includes a radial core 182joined to an axially extending, radially diffusing tip flag core 184.Although shown as a single core body, those of skill in the art willappreciate that in some embodiments the radial core 182 and the radiallydiffusing tip flag core 184 may be formed from separate bodies orstructures. The radial core 182 extends radially from the root region 96toward the tip region 98 and defines the forward radial flow cavity 138.The radial core 182 is spaced apart from the leading edge hybrid skincore 160.

The radially diffusing tip flag core 184 extends axially from the radialcore 182 proximate the leading edge 100 toward the trailing edge 102.The radially diffusing tip flag core 184 is oriented generallyperpendicular to the radial core 182. The radial core 182 forms theforward radial flow cavity 138 within the airfoil body 90 that extendsfrom the root region 96 toward the tip region 98, but does not exitthereon. That is, the forward radial flow cavity 138 does not extend thefull radial length of the airfoil body 90.

The radially diffusing tip flag core 184 defines a radially diffusingtip flag cavity 139 that is located within and immediately adjacent tothe tip region 98 and extends over the serpentine flow cavities 140,142, 144. The radially diffusing tip flag cavity 139 is spaced apartfrom the leading edge 100 and extends towards the trailing edge 102. Theradially diffusing tip flag cavity 139 is in fluid communication withthe forward radial flow cavity 138. The radially diffusing tip flagcavity 139 is at least partially defined between the rib 112, the firstwall 120, the third wall 124, and at least one of the tip shelf 110, thetip surface 126, and the pocket surface 128.

Referring to FIGS. 7-10, 13-16, and 18, the rib 112 is defined betweenthe radially diffusing tip flag cavity 139 and at least one of the firstserpentine flow cavity 140, the second serpentine flow cavity 142, andthe third serpentine flow cavity 144. The rib 112 is oriented at anangle relative to the tip shelf 110 of the airfoil 60 (i.e., notparallel). The rib 112 becomes progressively closer to at least one ofthe first serpentine flow cavity 140, the second serpentine flow cavity142, and the third serpentine flow cavity 144 in a direction thatextends from the leading edge 100 towards the trailing edge 102. Inother words, the rib 112 becomes disposed progressively farther awayfrom at least one of the tip shelf 110, the tip surface 126, and thepocket surface 128 in a direction that extends from the leading edge 100towards the trailing edge 102.

The rib 112 defines a radial diffusion angle of the radial diffusing tipflag cavity 139. The extent of the radial diffusion angle of the rib 112that at least partially defines the radially diffusing tip flag cavity139 is determined by establishing the optimal distribution of internalconvective heat transfer and cooling air heat pickup necessary tooptimize the local thermal cooling effectiveness while minimizing thelocal metal temperature gradient and relative metal temperaturedistribution between the radially diffusing tip flag cavity 139 and thefirst, second, and third serpentine flow cavities 140, 142, and 144respectively. The thermal management of pressure rise and cooling airtemperature heat pickup to the inlet portion of the radial diffusing tipflag cavity 139 is primarily governed by a volumetric flow rate throughthe forward radial flow cavity 138, and subsequent pressure andtemperature rise due to solid body pumping induced by the inertialforces generated by the rotation of the airfoil 60. The flow rate in theradially diffusing tip flag cavity 139 is a function of a pressure ratioat a junction between the forward radial flow cavity 138 and the tipflag cavity 139 and an exit of the tip flag cavity 139.

The radial diffusing tip flag core 184 and/or the radially diffusing tipflag cavity 139 has a radial height H that is measured between the rib112 and at least one of the tip surface 126, the tip shelf 110, or thepocket surface 128 of the tip squealer pocket 114. The radial height Hincreases in a direction that extends from the leading edge 100 towardthe trailing edge 102. In some embodiments, the radial height H of theradial diffusing tip flag core 184 and/or the radial diffusing tip flagcavity 139 at the trailing edge 102 is greater than the radial height Hof the radial diffusing tip flag core 184 and/or the radial diffusingtip flag cavity 139 at the junction between the radial core 182 (theforward radial flow cavity 138) and the radial diffusing tip flag core184 (the radial diffusing tip flag cavity 139). That is, the radialheight H of the radial diffusing tip flag core 184 (the radial diffusingtip flag cavity 139) at an end away from a junction with the radial core182 (the forward radial flow cavity 138) is greater than the radialheight H of the radial diffusing tip flag core 184 (the radial diffusingtip flag cavity 139) at the junction.

The increasing radial height H of the radial diffusing tip flag cavity139 arranges the radial diffusing tip flag cavity 139 as a radiallydiffused tip flag cavity having a constant, gradually increasing, and/orgradually decreasing flow area as the radial diffusing tip flag cavity139 extends from the forward radial flow cavity 138 toward the trailingedge 102. A rate of flow area convergence within the radial diffusingtip flag cavity 139 is defined by the angle of the rib 112 and by ataper in the aerodynamic shape of the airfoil body 90 as the airfoilbody 90 narrows toward the trailing edge 102 (e.g., as shown in FIGS.5-6). That is, a narrowing of the airfoil body 90 is achieved by areduction in a relative distance between the pressure side 92 (the firstwall 120) and the suction side 94 (the third wall 124) as the two sides(walls) each progress toward the trailing edge 102. The flow areadistribution of the radially diffusing tip flag cavity 139 is dictatedby the desired internal pressure loss, heat transfer, and cooling heatpickup necessary to optimally tailor the convective and film coolingadjacent to the pressure side 92 and suction side 94 surfaces as afunction of the external heat flux distribution and metal temperaturerequirements to achieve durability life goals.

The radial diffusing tip flag cavity 139 may be provided with internalconvective heat transfer features such as, for example, trip strips,turbulators, pedestals, and/or pin fins to tailor local thermal coolingeffectiveness in order to mitigate local heat load distributions alongthe local tip airfoil pressure side 92, the suction side 94, and the tipregion 98.

The radial diffusion of the radial diffusing tip flag cavity 139facilitates a more efficient utilization of the cooling air that isreceived within the forward radial flow cavity 138. Additionally, theshielding of the forward radial flow cavity 138 by the other cavities(e.g., as described above) provides locally colder cooling air thatenables a relatively high cooling potential due to the greatertemperature difference that exists between a hot external mainstreamflow and the colder internal air within the radial diffusing tip flagcavity 139. The increased temperature differential, as well as thehigher internal convective cooling heat transfer enables a greaterreduction in local material temperatures proximate the tip region 98and/or proximate the radial diffusing tip flag cavity 139 with lowercooling mass flow rates which in turn may improve efficiency of theturbine section 28. Furthermore, the radial diffusion of the radialdiffusing tip flag cavity 139 more efficiently cools the pressure side92 and the suction side 94 of the airfoil 60 proximate the tip region 98that is relatively close to the trailing edge 102.

As shown in FIGS. 16 and 18, an alternative configuration of a corestructure in accordance with an embodiment of the present disclosure isshown. In this embodiment, the rib 112 that will be defined between thetip flag core 184 and portions of the serpentine core 200 (e.g. thefirst upward pass core 206, the first downward pass core 208, the secondupward pass core 210) may be curvilinear, may be provided with multipleinflections, and/or diffusion angles. The rib 112 may be generallyhorizontal or upwardly extending.

Referring back to FIGS. 7-10, 13-16, and 18, the radial diffusing tipflag core 184 may define trailing edge slots 196. Cooling air that flowsthrough the forward radial flow cavity 138 is bled through the radialdiffusing tip flag cavity 139 and subsequently the trailing edge slots196.

Referring to FIG. 6, the first serpentine flow cavity 140, the secondserpentine flow cavity 142, and the third serpentine flow cavity 144 maybe fluidly connected to each other. The first serpentine flow cavity140, the second serpentine flow cavity 142, and the third serpentineflow cavity 144 extend between the root region 96 and the tip region 98.The radial diffusing tip flag cavity 139 is located between the tipshelf 110 and/or the tip squealer pocket 114 and the first serpentineflow cavity 140, the second serpentine flow cavity 142, and the thirdserpentine flow cavity 144, and fluidly separated therefrom. However,those of skill in the art will appreciate that one or more of theserpentine cavities 140, 142, 144 may be fluidly connected to the radialdiffusing tip flag cavity 139 by one or more bleed ports or otherstructures. As shown in FIGS. 8, 9, 13, 14, and 16, the forward radialflow cavity 138 is at least partially radially and axially disposedabout the first serpentine flow cavity 140, the second serpentine flowcavity 142, and the third serpentine flow cavity 144.

The first serpentine flow cavity 140, the second serpentine flow cavity142, and the third serpentine flow cavity 144 are each located betweenthe pressure side 92 and the suction side 94 and generally within thecentral portion of the airfoil body 90. The first serpentine flow cavity140, the second serpentine flow cavity 142, and the third serpentineflow cavity 144 are each axially disposed between the forward radialflow cavity 138 and the trailing edge slot 146.

The first serpentine flow cavity 140, the second serpentine flow cavity142, and the third serpentine flow cavity 144 are each fluidly connectedto a serpentine inlet cavity. In some embodiments, the serpentine inletcavity is configured as a dual serpentine inlet cavity. The firstserpentine flow cavity 140, the second serpentine flow cavity 142, andthe third serpentine flow cavity 144 receive cooling air from theserpentine inlet cavity to cool the airfoil body 90. The cooling airflows through the first serpentine flow cavity 140, the secondserpentine flow cavity 142, and the third serpentine flow cavity 144 andthe cooling air is discharged from the third serpentine flow cavity 144through the trailing edge slot 146 that is disposed adjacent to and isfluidly connected to the third serpentine flow cavity 144.

The total serpentine stream wise length of the first serpentine flowcavity 140, the second serpentine flow cavity 142, and the thirdserpentine flow cavity 144 are reduced due to the radially diffused tipflag cavity 139. As shown in FIG. 7, for example, the radial length ofeach serpentine flow cavity may lessen from the leading edge to thetrailing edge.

Referring to FIGS. 7-9, 13, 14, 16, and 18, the first serpentine flowcavity 140, the second serpentine flow cavity 142, and the thirdserpentine flow cavity 144 are formed by a serpentine core 200. Theserpentine core 200 may be used during a manufacturing process to formthe first serpentine flow cavity 140, the second serpentine flow cavity142, and the third serpentine flow cavity 144 within an airfoil body 90.In accordance with some embodiments, the manufacturing process is acasting process, although other advanced additive manufacturingprocesses, may be utilized to fabricate ceramic silica or alumina corebodies and/or directly additively manufacture airfoil geometries usingnickel based powders to produce form blade airfoil internal coolinggeometries and design configurations, may be employed to form blades andairfoils in accordance with embodiments of the present disclosure.

The serpentine core 200 includes a first serpentine trunk 202, a secondserpentine trunk 204, a first upward pass core 206, a first downwardpass core 208, and a second upward pass core 210. The first serpentinetrunk 202 extends radially toward the first upward pass core 206 and thesecond upward pass core 210. The second serpentine trunk 204 is spacedapart from and is disposed parallel to the first serpentine trunk 202.The second serpentine trunk 204 extends toward the first upward passcore 206. The first serpentine trunk 202 and the second serpentine trunk204 define the serpentine inlet cavity.

The first upward pass core 206 extends radially from at least one of thefirst serpentine trunk 202 and the second serpentine trunk 204. Thefirst upward pass core 206 extends radially and axially towards theforward radial flow core 180. The first upward pass core 206 has aprofile that is complementary to the profile of the radial core 182.

The first downward pass core 208 extends axially and radially from thefirst upward pass core 206. The first downward pass core 208 extendsradially towards the first serpentine trunk 202 and the secondserpentine trunk 204. The first downward pass core 208 is disposedbetween the first upward pass core 206 and the second upward pass core210.

The second upward pass core 210 extends radially and axially from thefirst downward pass core 208 towards the trailing edge slot 146. Thetrailing edge slot 146 extends radially and axially from the secondupward pass core 210.

The pressure side hybrid skin core 150, the leading edge hybrid skincore 160, the suction side hybrid skin core 170, the forward radial flowcore 180, and the serpentine core 200 define an airfoil core assembly.The airfoil core assembly is used to form cavities within an airfoil 60during a manufacturing process for forming the airfoil.

As used herein, the term “about” is intended to include the degree oferror associated with measurement of the particular quantity based uponthe equipment available at the time of filing the application. Forexample, “about” may include a range of ±8% or 5%, or 2% of a givenvalue.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,element components, and/or groups thereof.

While the present disclosure has been described with reference to anillustrative embodiment or embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe present disclosure. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this present disclosure, but that the present disclosurewill include all embodiments falling within the scope of the claims.

What is claimed is:
 1. A core assembly for manufacturing an airfoil of agas turbine engine, the core assembly comprising: an aft flowingserpentine hybrid skin core positioned relative to a plurality of corebodies and configured to define at least one serpentine cavity withinthe manufactured airfoil; wherein the aft flowing serpentine hybrid skincore extends from a root region toward a tip region in a radialdirection of the manufactured airfoil; and the plurality of core bodiesare positioned about the aft flowing serpentine hybrid skin core to forma shielding structure to thermally shield the aft flowing serpentinehybrid skin core in the manufactured airfoil.
 2. The core assembly ofclaim 1, wherein the plurality of core bodies includes a radial flowcore located axially forward the aft flowing serpentine hybrid skincore.
 3. The core assembly of claim 1, wherein the aft flowingserpentine hybrid skin core includes a first upward pass core, a firstdownward pass core, and a second upward pass core.
 4. The core assemblyof claim 3, wherein the first upward pass core is a hybrid skin core andthe first downward pass core and the second upward pass core areconvention cores.
 5. The core assembly of claim 1, wherein the aftflowing serpentine hybrid skin core includes structures to form internalconvective heat transfer augmentation features within a cavity formedthereby.
 6. The core assembly of claim 5, wherein the internalconvective heat transfer augmentation features include at least one oftrip strips, turbulators, pin fins, or pedestals.
 7. The core assemblyof claim 1, wherein the plurality of core bodies comprise: a pressureside hybrid skin core having a first trunk and a first branch thatextends from the first trunk; a suction side hybrid skin core spacedapart from the pressure side hybrid skin core; a leading edge hybridskin core is circumferentially located between the pressure side and thesuction side; and a radial flow core located between the pressure sidehybrid skin core, the suction side hybrid skin core, and the leadingedge.
 8. The core assembly of claim 7, wherein the radial flow coreincludes a radial core that is disposed generally parallel to at leastone of the pressure side hybrid skin core, the suction side hybrid skincore, and the leading edge hybrid skin core, wherein the radial core ispositioned between the aft flowing serpentine hybrid skin core and theleading edge hybrid skin core.
 9. The core assembly of claim 8, whereinthe radial flow core includes a radial diffusing tip flag core thatextends from the radial core in a direction away from the leading edgehybrid skin core and is positioned radially above the aft flowingserpentine hybrid skin core.
 10. The core assembly of claim 9, whereinthe radial diffusing tip flag core has an increasing radial heightdimension as the radial diffusing tip flag core extends away from theradial flow core, and the aft flowing serpentine hybrid skin coredecreases in radial height as the radial height dimension increases. 11.The core assembly of claim 1, wherein the aft flowing serpentine hybridskin core includes a structure to form a trailing edge slot in themanufacturing airfoil.
 12. An airfoil for a gas turbine engine, theairfoil comprising: an airfoil body having a leading edge, a trailingedge, a root region, and a tip region, wherein a direction from the rootregion to the tip region is a radial direction and a direction from theleading edge to the trailing edge is an axial direction; a hybrid aftflowing serpentine cavity formed within the airfoil body and defining acooling flow path within the airfoil body and defining a cooling flowpath extending between a root region to a tip region of the airfoil; anda plurality of cooling cavities formed within the airfoil body andpositioned about the hybrid aft flowing serpentine cavity to form ashielding structure within the airfoil body forward of the hybrid aftflowing serpentine cavity.
 13. The airfoil of claim 12, wherein theplurality of cooling cavities includes a radial flow cavity locatedaxially forward the hybrid aft flowing serpentine cavity.
 14. Theairfoil of claim 12, wherein the hybrid aft flowing serpentine cavityincludes a first upward pass, a first downward pass, and a second upwardpass.
 15. The airfoil of claim 14, wherein the first upward pass core isa hybrid skin core cavity and the first downward pass and the secondupward pass are conventional cavities.
 16. The airfoil of claim 12,wherein the hybrid aft flowing serpentine cavity includes internalconvective heat transfer augmentation features.
 17. The airfoil of claim16, wherein the internal convective heat transfer augmentation featuresinclude at least one of trip strips, turbulators, pin fins, orpedestals.
 18. The airfoil of claim 12, wherein the plurality of coolingcavities comprise: a pressure side hybrid skin core cavity locatedwithin the airfoil body on a pressure side relative to the hybrid aftflowing serpentine cavity; a suction side hybrid skin core cavity spacedapart from the pressure side hybrid skin core cavity and located withinthe airfoil body on a suction side relative to the hybrid aft flowingserpentine cavity; a leading edge hybrid skin core cavity iscircumferentially located between the pressure side and the suctionside; and a radial flow core located between (1) the pressure sidehybrid skin core and the suction side hybrid skin core and (2) betweenthe leading edge hybrid skin core cavity and the hybrid aft flowingserpentine cavity.
 19. The airfoil of claim 18, wherein the radial flowcore cavity defines a flow cavity that is generally parallel to at leastone of the pressure side hybrid skin core cavity, the suction sidehybrid skin core cavity, and the leading edge hybrid skin core cavity.20. The airfoil of claim 12, further comprising a trailing edge slotfluidly connected to the hybrid aft flowing serpentine cavity at thetrailing edge of the airfoil body.